Polymeric Materials in Speciation Analysis Based on Solid-Phase Extraction

Speciation analysis is a relevant topic since the (eco)toxicity, bioavailability, bio (geo)chemical cycles, and mobility of a given element depend on its chemical forms (oxidation state, organic ligands, etc.). The reliability of analytical results for chemical species of elements depends mostly on the maintaining of their stability during the sample pretreatment step and on the selectivity of further separation step. Solid-phase extraction (SPE) is a matter of choice as the most suitable and widely used procedure for both enrichment of chemical species of elements and their separation. The features of sorbent material are of great importance to ensure extraction efficiency from one side and selectivity from the other side of the SPE procedure. This review presents an update on the application of polymeric materials in solid-phase extraction used in nonchromatographic methods for speciation analysis.

New ion-imprinted polymer for selective removal of Cu2+ ion in aqueous solution using extracted Aloe vera leaves as a monomer

The objective of this project is to create a unique type of polymer known as an ion imprinted polymer (IIP) and a non-imprinted polymer (NIP) utilizing natural waste biosorbent materials. One example of this type of waste is Aloe vera, a plant with many medicinal uses that is grown globally. Aloe vera is considered one of the most valuable medicinal plants with a wide range of applications. Extracted Aloe vera was used as functional monomers for the first time to prepare new IIPs, epichlorohydrin, and Cu²⁺ ion as the cross-linking agent and template, respectively. The NIP was also synthesized for comparison, without the use of the Cu²⁺ salt. Following polymerization, the IIP particles were cleansed of template ions through a 0.1 M EDTA leaching process, resulting in the formation of cavities within the particles, these cavities in the polymer provide selective linking zones for these specific template ions. The synthesized IIPs were characterized using the most recent identification instruments. The experimental parameters for adsorption, such as pH of a solution, contact time, initial copper concentration, adsorbent dosage, and temperature have been optimized. The most effective conditions for metal adsorption onto the ionic imprinted polymer were found to be a pH of 8.0, a temperature of 30 °C, a concentration of 0.03 g/100 mL, and a contact time of 50 min. Based on the ANOVA statistical value, the adsorption of Cu²⁺ ion on IIP is significant with very low probability (p) values (<0.001). The Langmuir isotherm model and a second-order reaction were both used in the adsorption process. According to thermodynamic characteristics, Cu²⁺ adsorption over IIPs and NIP was an endothermic, spontaneous process. Compared to NIP, the imprinted polymer exhibits a significantly better capacity and selectivity for Cu²⁺ adsorption, the maximum removal percentage of IIPs and NIP was 96.02 % and 74.3 % respectively. Moreover, the research showed that ion imprinting can be a promising technique for preparing selective adsorbents to separate and preconcentrate metal in a medium of multiple competitive metals (Co²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Fe²⁺, and Pb²⁺) The most important point for this new Cu²⁺-IIPs was shown superior reusability up to 8 cycles with small decrees in uptake capability.

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

Novel thermo and ion-responsive copolymers based on metallo-base pair directed host-guest complexation for highly selective recognition of Hg2+ in aqueous solution

The development of materials with highly selective recognition towards Hg²⁺ is of great significance in environmental monitoring. Herein, a novel thermo-responsive copolymer with Hg²⁺ recognition property is prepared via thermally-initiated copolymerization of 5'-O-Acryloyl 5-methyl-uridine (APU) and N-isopropylacrylamide (NIPAM). The chemical structure and stimuli-sensitive properties of poly(N-isopropylacrylamide-co-5-methyl-uridine) (P(NIPAM-co-APU)) linear polymers and hydrogel are thoroughly investigated. At the supramolecular level, P(NIPAM-co-APU) linear polymers could respond to both temperature and Hg²⁺ stimuli with highly selective recognition towards Hg²⁺ over other 18 metal ion species (at least 5 fold difference) and common anions. Upon capturing Hg²⁺ by APU units as host metal receptors, the lower critical solution temperature (LCST) of P(NIPAM-co-APU, PNU-7 and PNU-11) linear polymers are significantly shifted more than 10 °C due to the formation of stable APU-Hg²⁺-APU directed host-guest complexes. Accordingly, at the macroscopic level, P(NIPAM-co-APU) hydrogel display selective and robust recognition of Hg²⁺ under optimum conditions, and its maximum Hg²⁺ uptake capacity was 33.1 mg g^-1. This work provides a new option for Hg²⁺ recognition with high selectivity, which could be facilely integrated with other smart systems to achieve satisfactory detection of environmental Hg²⁺.

Colorimetric detection of heavy metal ions with various chromogenic materials: Strategies and applications

Detection of heavy metal ions has drawn significant attention in environmental and food area due to their threats to the human health and ecosystem. Colorimetry is one of the most frequently-used methods for the detection of heavy metal ions owing to its simplicity, easy operation and rapid on-site detection. The development of chromogenic materials and their sensing mechanisms are the key research direction in the area of colorimetric method. Since each chromogenic material has their unique optical and chemical properties, they have totally different colorimetric sensing mechanisms. This review focuses on the chromogenic materials and their sensing strategies for the colorimetric detection of heavy metal ions. We divide the chromogenic materials into three types, including organic materials, inorganic materials, and other materials. As for each type of chromogenic material, we discuss their detailed sensing strategies, sensing performance, and real sample applications. Moreover, current challenges and perspectives related to the colorimetry of heavy metal ions are also discussed in this review. The aim of this review is to help readers to better understand the principles of colorimetric methods for heavy metal ions and push the development of rapid detection of heavy metal ions.

From Classical to Advanced Use of Polymers in Food and Beverage Applications

Polymers are extensively used in food and beverage packaging to shield against contaminants and external damage due to their barrier properties, protecting the goods inside and reducing waste. However, current trends in polymers for food, water, and beverage applications are moving forward into the design and preparation of advanced polymers, which can act as active packaging, bearing active ingredients in their formulation, or controlling the head-space composition to extend the shelf-life of the goods inside. In addition, polymers can serve as sensory polymers to detect and indicate the presence of target species, including contaminants of food quality indicators, or even to remove or separate target species for later quantification. Polymers are nowadays essential materials for both food safety and the extension of food shelf-life, which are key goals of the food industry, and the irruption of smart materials is opening new opportunities for going even further in these goals. This review describes the state of the art following the last 10 years of research within the field of food and beverage polymer's applications, covering present applications, perspectives, and concerns related to waste generation and the circular economy.

Bio-Inspired Imprinting Materials for Biomedical Applications

Inspired by the recognition mechanism of biological molecules, molecular imprinting techniques (MITs) are imparted with numerous merits like excellent stability, recognition specificity, adsorption properties, and easy synthesis processes, and thus broaden the avenues for convenient fabrication protocol of bio-inspired molecularly imprinted polymers (MIPs) with desirable functions to satisfy the extensive demands of biomedical applications. Herein, the recent research progress made with respect to bio-inspired imprinting materials is discussed in this review. First, the underlying mechanism and basic components of a typical molecular imprinting procedure are briefly explored. Then, emphasis is put on the introduction of diverse MITs and novel bio-inspired imprinting materials. Following these two sections, practical applications of MIPs in the field of biomedical science are focused on. Last but not least, perspectives on the remaining challenges and future development of bio-inspired imprinting materials are presented.

Molecularly Imprinted Affinity Membrane: A Review

A molecularly imprinted affinity membrane (MIAM) can perform separation with high selectivity due to its unique molecular recognition introduced from the molecular-printing technique. In this way, a MIAM is able to separate a specific or targeted molecule from a mixture. In addition, it is possible to achieve high selectivity while maintaining membrane permeability. Various methods have been developed to produce a MIAM with high selectivity and productivity, with their respective advantages and disadvantages. In this paper, the MIAM is reviewed comprehensively, from the fundamentals of the affinity membrane to its applications. First, the development of a MIAM and various preparation methods are presented. Then, applications of MIAMs in sensor, metal ion separation, and organic compound separation are discussed. The last part of the review discusses the outlook of MIAMs for future development.

A Pyrazolo Imine-based Colorimetric and Turn-on Fluorescent Sensor Probe for Determination of Hg2+ Ion and its Application in Test Paper Strips

In this work, we synthesized diethylamino substituted pyrazolo imine (3) fluorescent probe for recognition of Hg²⁺ ion.The sensor probe 3 can detect Hg²⁺ by colorimetric method, and there is a 10-fold enhancement in fluorescence response. When the fluorescent probe bound with Hg²⁺ ion, turn-on fluorescence was observed via the coordination. Probe 3 has an excellent selectivity toward Hg²⁺ in the CH₃ CN/H₂ O (8:2, v/v) solution with low limit of detection and high binding association constant of 551 parts per billion (ppb) and 6.6067 × 10⁶  m^-1 for 3+Hg²⁺ , respectively. Furthermore, the formation of 3+Hg²⁺ complex with 1:1 binding mode was evidenced by Job's plot, ¹ H NMR spectroscopy and Mass analysis. In addition, probe 3 is a feasible option to detect Hg²⁺ in various sources of water samples. Bio-imaging experiments have demonstrated that probe 3 can be used to monitor Hg²⁺ in Escherichia coli bacterial cell. The sensor 3 was also used for paper strip application to detect Hg²⁺ ion.

(Macro)Molecular Imprinting of Proteins on PCL Electrospun Scaffolds

Biological recognition sites are very useful for biomedical purposes and, more specifically, for polymeric scaffolds. However, synthetic polymers are not capable of providing specific biological recognition sites. To solve this inconvenience, functionalization of biological moieties is typically performed, oftentimes via peptide binding. In this sense, the main task is capturing the biological complexity of a protein. This study proposes a possible alternative solution to this challenge. Our approach is based on the combination of molecular imprinting (MI) and electrospinning processes. We propose here an alternative MI approach with polymeric structures, instead of using cross-linkers and monomers as conventionally performed. Different PCL-protein scaffolds were produced via electrospinning before performing MI. Gelatin, collagen, and elastin were used as proteins. Results evidenced that the MI process conducted with PCL electrospun membranes was carried out with ionic interactions between the desired molecules and the recognition sites formed. In addition, it has been proved that MI was more efficient when using gelatin as a template. This approach opens a new stage in the development of recognition sites in scaffolds obtained with synthetic polymers and their application for biomedical purposes.

A novel multidentate pyridyl ligand: A turn-on fluorescent chemosensor for Hg2+ and its potential application in real sample analysis

A novel pyridyl-based ligand with multiple binding sites was developed as potential turn on fluorescent probe for mercuric ion. In comparison with other transition metal ions, the ligand displayed a significant optical selectivity and sensitivity for Hg²⁺ in aqueous solution with a remarkable fluorescence enhancement. The obtained spectroscopic response was related to the inhibition of the photo-chemical mechanism known as photo-induced electron transfer (PET) in the ligand and CN isomerization by Hg²⁺ binding. A good linearity between fluorescence responses and Hg²⁺ concentration was obtained in the range 3.3 × 10^-9 M-1.6 × 10^-8 M and a nanomolar level limit of detection (LOD) (1.4 × 10^-9 M ~ 0.28 ppb) and limit of quantification (LOQ) (4.8 × 10^-9 M ~ 0.93 ppb) were obtained. Both LOD and LOQ values are very low compared to the reported permissible Hg²⁺ level in drinking water (2 ppb) by US Environmental Protection Agency (EPA). The possible binding mode between ligand and Hg²⁺ were determined using Job's plot analysis and density functional theory (DFT) calculations and a complex with 1:1 stoichiometric ratio was suggested. The response of the pyridyl ligand upon Hg²⁺ addition was noted to be fast without any time delay and reversible. The performance of the ligand at nanomolar level of Hg²⁺ and real sample application of the proposed method was investigated and satisfactory results were obtained.

Mercury speciation in edible seaweed by liquid chromatography - Inductively coupled plasma mass spectrometry after ionic imprinted polymer-solid phase extraction

In contrast to most of essential and heavy metals, mercury levels in seaweed are very low, and pre-concentration methods are required for an adequate total mercury determination and mercury speciation in this foodstuff. An ionic imprinted polymer-based solid phase extraction (on column) pre-concentration procedure has been optimized for mercury species enrichment before liquid chromatography hyphenated with inductively coupled plasma mass spectrometry determination. The polymer has been synthesized by the precipitation polymerization method and using a ternary pre-polymerization mixture containing the template (methylmercury), a non-vinylated monomer (phenobarbital), and a vinylated monomer (methacrylic acid). Factors affecting the adsorption/desorption of Hg species (extract pH, loading and elution flow rates, volume of eluent, etc.), and parameters such as breakthrough volume and reusability, were fully studied. Mercury species were first isolated from seaweed by ultrasound assisted extraction using a 0.1% (v/v) HCl, 0.12% (w/v) l-cysteine, 0.1% (v/v) mercaptoethanol solution. Under optimized conditions, the limits of detection were 0.007 and 0.02 μg kg^-1 dw for methylmercury and Hg(II), respectively. The pre-concentration factor (volume of 10 mL of seaweed extract) was 50. Repeatability and reproducibility of the method were satisfactory with relative standard deviations lower than 16%. The proposed methodology was finally applied for the selective pre-concentration and determination of methylmercury and Hg (II) in a BCR-463 certified reference material and in several edible seaweeds.

A Critical Review on the Synthesis and Application of Ion-Imprinted Polymers for Selective Preconcentration, Speciation, Removal and Determination of Trace and Essential Metals from Different Matrices

The presence of toxic trace metals and high concentrations of essential elements in the environment presents a serious threat to living organism. Various methods have been used for the detection, preconcentration and remediation of these metals from biological, environmental and food matrices. Owing to the complexicity of samples, methods with high selectivity have been used for detection, preconcentration and remediation of these trace metals. These methods are achieved by the use of ion-imprinted polymers (IIPs) due to their impressive properties such as selectivity, high extraction efficiency, speciation capability and reusability. Because of the increase of toxic trace and essential metals in the environment, IIPs have attracted great use in analytical chemistry. This review, provide a brief background on IIPs and polymerization method that are used for their preparation. Recent applications of IIPs as adsorbents for preconcentration, removal, speciation and electrochemical detection of trace and essential metal is also discussed.

A New Highly Selective Colorimetric and Fluorometric Coumarin-based Chemosensor for Hg2

A novel colorimetric and fluorometric method based on coumarin as signalling unit was developed for Hg²⁺ recognition and quantification. Initially, the alkyne functionality was incorporated into a coumarin system and the resulting molecule showed higher specificity and sensitivity for Hg²⁺ over other cations in both absorption and emission sensing assays. The Hg²⁺ recognition was detected as visible colour change from colourless to yellow and as fluorescence quenching. The colour change was assigned to the increased intramolecular charge transfer (ICT) in the signalling unit upon Hg²⁺ binding whereas a decline in the fluorescence intensity was ascribed to the heavy atom effect from Hg²⁺. In order to generate a material with high sensing performance level, alkyne-functionalized molecule was hosted into a polymeric material. The resulting functionalized polymer showed higher sensitivity and selectivity for Hg²⁺ over its corresponding coumarin molecule. The investigation of the possible binding modes for Hg²⁺ suggested both alkyne and triazole functionalities as potential binding sites for Hg²⁺. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were evaluated and values less than a recommended maximum level of Hg²⁺contaminant in drinking water (2.00 μg/L) were obtained (LOD = 0.44 μg/L and LOQ = 1.33μg/L). The real-life application of the method was investigated using natural water samples containing Hg²⁺ levels equivalent to the maximum tolerable concentration of Hg²⁺ in drinking water. The outcomes suggested that the method could be used in the sensing and determination of Hg²⁺ level of contaminant in the environment.

Progressive trends in heavy metal ions and dyes adsorption using silk fibroin composites

Thriving industrialization for human lifestyle headway has seeded the roots of water intoxication with harmful and hazardous toxic metal ions and dyes, which may ingress into food chains and become homicidal or mutation causing for creatures. The degummed functionalized silk fibroin composites with different biomaterials and synthetic materials are able to show adsorption efficiencies equivalent to 52.5%, 90%, 81.1%, 93.75%, 84.2%, and 98.9% for chromium, copper, cadmium, lead, thorium, and uranium ions, respectively, and adsorption capacity of 88.5 mg/g, 74.63 mg/g, 76.34 mg/g, and 72 mg/L for acid yellow 11, naphthol orange, direct orange S, and methylene blue, respectively, which make them desirable solution for water toxicants removal. This review is intended to describe the ability of silk fibroins to adsorb and abolish toxic heavy metal ions and dyes from water reservoirs, thus, providing a way to step toward water sanitation and wholesome living. Graphical abstract.

Molecularly Imprinted Sites Translate into Macroscopic Shape-Memory Properties of Hydrogels

The polymerization of acrylamide, dopamine methacrylamide, and bis-acrylamide in the presence of one of the electron acceptors, N,N'-dimethyl-4,4'-bipyridinium, (1), N,N'-dimethylbipyridinium-4,4'-ethylene, (2), or bipyridinium dithienylethene, (3), yields hydrogel matrices of high stiffness that are cooperatively cross-linked by bis-acrylamide and electron donor (dopamine)-acceptor complexes. Washing off the diffusional electron acceptor units yields molecularly imprinted matrices of lower stiffness, stabilized only by the bis-acrylamide bridges that include specific binding sites for the selective association of the electron acceptor (1), (2), or (3). These imprinted hydrogel matrices show selective recovery of the stiff properties upon binding the respective electron acceptor units to the imprinted sites. The control over the stiffness properties enables the development of shape-memory, molecularly imprinted hydrogels and stiffness-based sensors. The results show how molecularly imprinted sites translate into macroscopic shape-memory properties of hydrogels.

Green multi-functional monomer based ion imprinted polymers for selective removal of copper ions from aqueous solution

Green ion imprinted polymers (IIPs) were prepared in aqueous phase via the synergy of three functional monomers of low-cost eco-friendly gelatin (G), 8-hydroxyquinoline (HQ) and chitosan (C), namely G-HQ-C IIPs, and were applied as an effective and recyclable adsorbent to remove Cu(II) from aqueous solution. The as-prepared G-HQ-C IIPs were systematically characterized, and several major factors affecting adsorption capacity including solution pH, temperature and contact time were investigated in detail. The adsorption of Cu(II) on G-HQ-C IIPs followed the pseudo-second-order kinetic and Langmuir isotherm models, and the adsorption capacity increased with temperature increase. Moreover, the maximum adsorption capacities of G-HQ-C IIPs toward Cu(II) reached up to 111.81 mg/g at room temperature, much higher than those of most of the reported adsorbents for Cu(II). The G-HQ-C IIPs displayed excellent selectivity against seven common divalent ions with selectivity coefficients above 18.71, as well as high anti-interference ability. Additionally, a good reusability was demonstrated without significant loss in adsorption capacity after at least ten cycles. The IIPs were applied to environmental water samples for selective removal of Cu(II) with satisfactory results. By replacing Cu(II) template by Cd(II), Hg(II) and Pb(II), respectively, the obtained three kinds of IIPs based on G-HQ-C presented convincing imprinting properties, and therefore the work could provide a simple and general imprinting strategy toward various concerned heavy metal ions through multi-point interactions from multiple functional monomers.

A highly selective and sensitive ESIPT-based coumarin–triazole polymer for the ratiometric detection of Hg2+

A reversible ESIPT based system for the detection of Hg²⁺ was developed. The system exhibited better properties compared to that of recently developed ratiometric fluorescent systems.

Speciation Analysis of Trace Mercury in Sea Cucumber Species of Apostichopus japonicus Using High-Performance Liquid Chromatography Conjunction With Inductively Coupled Plasma Mass Spectrometry

In this paper, a simple and cost-effective method using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry with a rapid ultrasound-assisted extraction was used for analysis speciation of trace mercury in sea cucumber species of Apostichopus japonicus. The effective separation of inorganic mercury, methylmercury, and ethylmercury was achieved within 10 min using Agilent ZORBAX SB-C₁₈ analytical and guard columns with an isocratic mobile phase consisting of 8% methanol and 92% H₂O containing 0.12% L-cysteine (m/v) and 0.01 mol/L ammonium acetate. Mercury species were extracted from A. japonicus samples using a solution containing 2-mercaptoethanol, L-cysteine, and hydrochloric acid and sonicating for 0.5 h. The limits of detection of inorganic mercury, methylmercury, and ethylmercury were 0.12, 0.08, and 0.20 μg/L, and the minimum detectable concentrations (measured at 0.500 g sample volume in 10.00 mL) were 2.4, 1.6, and 4.0 μg/kg, respectively. Analysis of a scallop certified reference material (GBW 10024) revealed accordance between the experimental and certified values. This study provides a reference for the evaluation of mercury speciation in sea cucumber and other seafood.

Development of Cellulosic Paper-Based Test Strips for Mercury(II) Determination in Aqueous Solution

Titration method (dropping-on method) was introduced as an efficient approach for determining the mercury ion (Hg²⁺) concentration in aqueous solution by using fabricated cellulosic paper-based test strips. In this study, dithizone used as a recognition reagent was physically loaded on cellulosic paper-based test strips for Hg²⁺ selective recognition. The sensing mechanism was established on the spectral absorption rate of the coordination compound that was formed by dithizone and Hg²⁺ under strong acidic conditions. The calibration curve was obtained by the absorbency of Hg²⁺-dithizone complexes from different Hg²⁺ concentration solutions, and the correlation coefficient (R ²) reached 0.9971. The detection range of the test trip for Hg²⁺ was obtained at 0.1 μg/mL to 30 μg/mL. Moreover, these superior cellulosic paper-based test strips have a rapid color-forming time (1.5 min) and low volume demand (3.7 μL samples at 0.0127 g/L dithizone recognition concentration). This portable paper-based test strip can give potential applications for field screening or on-site semiquantitative analysis.

Nanopowder synthesis of novel Sn(II)-imprinted poly(dimethyl vinylphosphonate) by ultrasound-assisted technique: Adsorption and pre-concentration of Sn(II) from aqueous media and real samples

In this research, a novel Sn(II)-imprinted poly(dimethyl vinylphosphonate) nanopowder (Sn(II)-IPDMVPN) was prepared using Sn²⁺, dimethyl vinylphosphonate, azobis isobutyronitril and ethylene glycol dimethacrylate as the template, ligand, initiator and cross linker, respectively. The non-imprinted poly(dimethyl vinylphosphonate) nanopowder (NIPDMVPN) was also synthesized utilizing the same procedure without using SnCl₂·2H₂O in order to compare the results with the Sn(II)-IPDMVPN. The structure, morphology and composition of the products were characterized by XRD, SEM, EDX, XRF, BET, FT-IR and NMR techniques. Some experimental conditions including pH, eluent concentration and sample volume were optimized to maximize Sn(II) adsorption by the Sn(II)-IPDMVPN. It was found that the optimum conditions are pH = 5, 1.00 M of HNO₃ as eluent and sample volume up to 50 mL. The results obtained by ICP-MS indicated that the Sn(II)-IPDMVPN had much higher adsorption capacity for Sn(II) ions (about threefold) than the NIPDMVPN. The applicability of the Sn(II)-IPDMVPN was also investigated in three different real samples. Under the best experimental conditions, the calibration graphs were linear in the range of 0.19-90 μg L^-1 with a coefficient of determination (R²) of 0.990. The detection limit was calculated to be 0.06 μg L^-1. The relative standard deviation (RSD) for six replicate measurements of Sn(II) at 1.00 ng mL^-1 was determined to be 1.8%. The results showed that the Sn(II)-IPDMVPN-ICP-MS is a very simple, rapid, sensitive and efficient method for the determination of Sn(II) ions in water samples.

Molecularly imprinted polymers for the detection of illegal drugs and additives: a review

This review (with 154 refs.) describes the current status of using molecularly imprinted polymers in the extraction and quantitation of illicit drugs and additives. The review starts with an introduction into some synthesis methods (lump MIPs, spherical MIPs, surface imprinting) of MIPs using illicit drugs and additives as templates. The next section covers applications, with subsections on the detection of illegal additives in food, of doping in sports, and of illicit addictive drugs. A particular focus is directed towards current limitations and challenges, on the optimization of methods for preparation of MIPs, their applicability to aqueous samples, the leakage of template molecules, and the identification of the best balance between adsorption capacity and selectivity factor. At last, the need for convincing characterization methods, the lack of uniform parameters for defining selectivity, and the merits and demerits of MIPs prepared using nanomaterials are addressed. Strategies are suggested to solve existing problems, and future developments are discussed with respect to a more widespread use in relevant fields. Graphical abstract This review gives a comprehensive overview of the advances made in molecularly imprinting of polymers for use in the extraction and quantitation of illicit drugs and additives. Methods for syntheses, highlighted applications, limitations and current challenges are specifically addressed.

Fluorescence quenching of MoS2 nanosheets/DNA/silicon dot nanoassembly: effective and rapid detection of Hg2+ ions in aqueous solution

Mercury (Hg) contamination of aquatic sites represents a serious risk for human health and the environment. Therefore, effective and rapid monitoring of Hg in aqueous samples is a challenge of timely importance nowadays. In the present study, a rapid and sensitive mercury sensor based on the fluorescence quenching of MoS₂ nanosheets/DNA/silicon dot nanoassembly has been developed for the efficient detection of mercury(II) in aquatic environments. In this process, silicon dots were synthesized through one-step high-temperature calcinations and thermomagnesium reduction method at 900 °C using rice husk as a silicon source, which demonstrates superior photophysical properties and excitation-dependent fluorescence behavior. The interaction between MoS₂ nanosheets/DNA/silicon dot nanoassembly and Hg²⁺ ions was studied using photoluminescence spectroscopy. The addition of Hg²⁺ ions to the assay solution induced the detachment of fluorescent probe from the surface of MoS₂ nanosheets. Thus, the fluorescent probes sustained its fluorescence intensity. The developed sensor was tested on various concentrations of Hg²⁺ ions ranging from 0 to 1000 nM as well as on various metal ions. In addition, MoS₂ nanosheets/DNA/silicon dot nanoassembly fluorescent Hg sensor efficiently detected the presence of Hg²⁺ ions in real-time water samples, which was comparably detected by the conventional atomic absorbance spectrometer (AAS). Overall, our results highlighted the high reliability of the present approach for environmental monitoring of Hg²⁺ ions, if compared to that of the customary method with a lowest detection limit of 0.86 nM.

Synthesis and characterization of a new ion-imprinted polymer for the selective separation of thorium(iv) ions at high acidity

A new ion-imprinted polymer (IIP), which was synthesized with bis(2-methacryloxyethyl) phosphate as functional ligand and Th⁴⁺ as a template ion, can be used in high acidity environment.

Surface Plasmon Resonance-Based Fiber Optic Sensors Utilizing Molecular Imprinting

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the analyte to be sensed. Sensors incorporating this technique along with surface plasmon or localized surface plasmon resonance (SPR/LSPR) provide highly sensitive real time detection with quick response times. Unfolding these techniques with optical fiber provide the additional advantages of miniaturized probes with ease of handling, online monitoring and remote sensing. In this review a summary of optical fiber sensors using the combined approaches of molecularly imprinted polymer (MIP) and the SPR/LSPR technique is discussed. An overview of the fundamentals of SPR/LSPR implementation on optical fiber is provided. The review also covers the molecular imprinting technology (MIT) with its elementary study, synthesis procedures and its applications for chemical and biological anlayte detection with different sensing methods. In conclusion, we explore the advantages, challenges and the future perspectives of developing highly sensitive and selective methods for the detection of analytes utilizing MIT with the SPR/LSPR phenomenon on optical fiber platforms.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Synthesis of multi-ion imprinted polymers based on dithizone chelation for simultaneous removal of Hg2+, Cd2+, Ni2+ and Cu2+ from aqueous solutions

A multi-ion imprinted polymer strategy based on dithizone chelation for simultaneous removal of multiple ions in aqueous solution.

Antimicrobial and toxicological evaluations of binuclear mercury(ii)bis(alkynyl) complexes containing oligothiophenes and bithiazoles

We investigated the antimicrobial activity of bis-(alkynyl)mercury(ii) complexes with oligothiophene and bithiazole linking units against MRSA and C. albicans, and their cytotoxicity was tested on NIH 3T3 cells.

Facile preparation of a novel Hg(ii)-ion-imprinted polymer based on magnetic hybrids for rapid and highly selective removal of Hg(ii) from aqueous solutions

This study reveals a facile strategy to prepare magnetic Hg(ii)-ion-imprinted polymers with incorporated Fe₃O₄@SiO₂ particles for rapid and efficient removal of Hg(ii) ions, due to the soft acid–soft base interaction of Hg(ii) and allylthiourea.

Synthesis of ion imprinted polymeric nanoparticles for selective pre-concentration and recognition of lithium ions

A new Li⁺–IIP has been prepared for the fast determination and selective separation of lithium ions in aqueous samples.